Faster payback despite higher investment?

By way of introduction, we would like to deal with the term amortisation, or more precisely, the amortisation period. We will limit ourselves to the so-called static amortisation, which means that a system generates the same financial return year after year. The focus here is not on the energetic amortisation, i.e. the question of when the energy that was needed to manufacture and install the system was recovered.

The static payback calculation itself is very simple: the payback period is the time by which the initial investment has been earned back. Or mathematically: payback period=acquisition costs/annual return.

Let's take a look at an example from Austria, the typical 5 kWp system on the roof of a house:

Figure 1: Analysis of the three calculation variants:

• Simulation without photovoltaic system
• Simulation with photovoltaic syste
• Simulation with photovoltaic system + my-PV solution

Figure 2: Simple calculation of the payback period in comparison without my-PV solution and with my-PV solution (despite additional investment).

A system without my-PV products would pay for itself within 9 years, i.e. it would be completely paid off. Sounds like a lot, but the lifespan of the system can be estimated at 30 years. This means that the system earns more than three times its value in its lifetime. We neglect the inflation of the electricity price, but do not include the operating costs of the system. This is quite feasible, especially because electricity price increases are very difficult to estimate.

If surplus photovoltaic power is mainly used for water heating and not for feeding into the grid, the annual savings amount to €729 instead of €546. The payback period is reduced to 8 years.

This effect is achieved because heating costs are replaced by the reduced feed-in yield. The very manageable additional investment of 1,000 euros thus pays for itself more quickly than the actual photovoltaic system. All in all, this means a shorter payback period.

A good tool to get to grips with the values is our Power-Coach, which you can use to play around and design your own system without any obligation and free of charge.